The difference between one-step injection stretch blowing and two-step moulding and their respective characteristics
Compared with the two-step method, the one-step process is completed in one piece of equipment, from raw materials to finished products.
The production process is simple, one-time moulding, its controllability is strong, the accuracy of the bottle mouth is high. And no secondary heating is required, so the energy consumption is low.
The two-step method requires injection moulding of the preform first and then secondary processing on the blow moulder machine to blow molding.
It is completed twice by an injection moulder machine and a blow moulder. It can be produced online or on separate lines.
What kind of applications are suitable for the one-step method and the two-step method:
The one-step process is more suitable for medium and small batches and products with high hygiene requirements. Of course, it has more significant advantages for special-shaped bottles and thick-walled bottles.
At present, one of the two-step methods is high-speed equipment, which is suitable for the mass production of water bottles and beverages.
One is low speed (or semi-automatic) for some small quantity products.
The following picture shows the bottle type that can be processed by the one-step method:
Features of one-step injection blow moulder equipment:
One-step blow moulder has three-station equipment, such as AOKI equipment. The three stations are preform injection moulding and temperature adjustment, stretch blow moulding, and product removal.
In addition to the three-station equipment, there is also four-station equipment, such as Nova’s equipment, which adds a cooling station to the original three-station equipment.
The ASB equipment has one more heating station based on three stations.
The materials suitable for one-step blow moulding are
PET, PP, PETG, PC, PCTG, HDPE, HIPS, PES, PEN, recycled PET, amorphous PET, etc.
Specifically, different materials should be selected according to the stretch ratio, blow-up ratio and specific application of different materials.
Choose different materials. The barrier properties of the bottles are also different. The following figure shows the application of different materials.
Injection stretch blowing of square PET bottle:
Square bottle design: the biaxial stretching ratio is limited, and the most difficult to solve is the R angle problem.
At present, the shoulder of the square bottle can be directly injection moulded on the preform.
Application of PPSU material: PPSU has relatively small stretch and unique material properties and is currently mainly used for feeding bottles.
How long does the one-step blow moulder production take
Depending on the product, the mould production time is generally 65 to 85 days, and mould adjustment time needs to be reserved.
One-step equipment currently has three stations and four stations. Each station has moulds, such as hot runners, mouth moulds (three sets), injection moulds, blow moulds, extension devices, etc.
The selection of mould materials for each station also has unique requirements, basically designated steel materials.
What is the extreme thickness of the bottle processed by the one-step method?
Depending on the different conditions of different materials, the minimum and maximum wall thicknesses of PET materials in the one-step method are 0.1mm and 1.2mm. The thicker the consistency, the transparency will decrease. For some materials with slow crystallization speed, such as PETG, PCTA, TRITAN and other materials, the thickness of the bottle wall can be 2mm.
When designing the preform, is there any method or software that can simulate the wall thickness distribution and resistance to pressure and thermal deformation of the bottle after blowing? What is the approximate accuracy?
CAE software can be used to simulate. If you are uncertain about the design, you can use cae software to simulate and analyze it. The colour is the thickness. At the same time, Cae can also affect the drop resistance. Be sure to provide accurate material parameters during simulation.
The Aoki Aoki machine should rely more on preform cooling in different positions. Can you share this aspect? That is, how to match and adjust the waterway design and the residual temperature?
AOKi equipment process, bottle forming is mainly formed by the residual temperature of the preform itself. The thin wall is cooled first, and the thick wall can be extended. Therefore, the forming of some heterosexual bottles can be carried out according to the principle of different cooling effects of different thicknesses of the preforms. Some products may also require hot kerosene cooling.
What process does the hot filling bottle need to achieve?
Generally, the bottle mouth of hot-filled products needs crystallization treatment. The body and bottom of the bottle are solved with a rib structure. The two-part method is easy to realize. The one-step process is more complicated. For the one-step bottle of standard material, the heat resistance limit is 65 degrees for 3 minutes.
The benefits of reheating during the moulding process are:
Purpose of reheating: mainly to recrystallize the material to enhance heat resistance and rigidity.
The inner wall of some PET bottles has relatively high tension, and the contents are prone to wall hanging. Is there any way to solve it?
At present, to completely solve this problem, it is basically necessary to use special coatings. It has been applied in the food industry, but price, compatibility and production line arrangement are problems. I know that the significant colour masterbatch factories worldwide are trying to do it. Still, there is no commercialization plan at present.
The bottles are prone to deformation when transported over long distances in the summer. What should I pay attention to?
PET bottles are generally easy to squeeze and deform above 60 degrees. The deformation may be related to the bottle shape. If the bottle shape cannot be changed, it is recommended to consider the packaging.
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